In celebration of their 70th anniversary, Paul Miller serenaded his wife with Bing Crosby’s “Let Me Call You Sweetheart.”

“They’re such great role models,” said their granddaughter Robin Vermeer Bobo, 50, who shared the video of the performance on Facebook. “No one has an easy life and they didn’t, but they were devoted to each other.”

Miller performed his romantic rendition of the love song when the preacher invited him to renew his vows at a party celebrating their 70 years of marriage.

Bobo told InsideEdition.com that the pair began dating in their teens, but his now-wife, Imogene Miller, “wasn’t going to marry him until he was a responsible man,” she said.

On Paul’s 20th birthday, they were married, and have been in love ever since.

“They’ve been together all of those years," Bobo said. "He sings to her a lot. He tells people she’s the most beautiful person he’s ever seen."

She explained that the Millers, who had two biological children of their own, took her and her family in when she was 2 years old, and her mother was pregnant.

Similarly, they took in many foster children after they were aged out of the system, growing their collection of adopted children and adopted grandchildren into the nearly 60 people that attended their vow renewals Thursday.

“It was so sweet,” Bobo recalled. “Their love is definitely a true love.”